[BUGFIX] Throw 404 error when XML sitemap is not available

Resolves: #97612
Releases: main, 11.5
Change-Id: Ia23a15f0beb864a8b53c568ed27642ec7ac8c7b2
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74868


Tested-by: core-ci <typo3@b13.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>